Sabot projectile



Filed July 28, 1967 2 Sheets-Sheet 1 Feb. 24, 1970 w. ENGEL 3,

SABO'I' PROJECTILE 22 In venfbf Wei/fer In 8/ 2 fifforn y s Feb. 24,1970 w. ENGEL SABOT PROJECTILE Filed July 28, 1967 2 Sheets-Sheet z n, vI I i h a 7 firms/776k Wa/fk' lzll ge/ 3,496,869 SABOT PROJECTILE WalterEngel, Dubendorf, Switzerland, assignor to Oerlikon-Buhrle Holding Ltd.,Zurich, Switzerland Filed July 28, 1967, Ser. No. 656,856 Int. Cl. F42b13/16 U.S. Cl. 102-93 7 Claims ABSTRACT OF THE DISCLOSURE The sabot of asabot projectile has a rear part, a jacket and a driving band. Jacketand driving band are made in a single piece, and the connection betweenthe rear part and the driving band with jacket is formed by adjacentcone surfaces whose apices point rearwards, so that the driving band ispressed against the rear part by the gas pressure. The outside diameterof the driving band is preferably greater than the greatest insidediameter of the gun bore from which the sabot projectile is fired.

The present invention concerns a sabot projectile and a gun bore fromwhich the projectile is fired.

An object of the invention is to provide a sabot projectile wherein thesabot is not destroyed by the gas pressure when the projectile is fired.

A further object of the invention is to provide a sabot projectilewherein the connection between the driving band of the sabot and thejacket and also the connection between the rear part and the drivingband are so designed that they are not destroyed by the gas pressurewhen the projectile is fired.

It is a further object of the invention to provide a sabot projectilewherein the said connections between driving band, jacket and rear partprevent any unwanted entry of gas when the projectile is fired.

With the above and other objects in view which will become apparent fromthe detailed description below, some preferred modifications of theinvention are shown in the drawings in which:

FIG. 1 shows a sectional view with parts in elevation through a sabotprojectile taken along section line II in FIG. 2;

FIG. 2 shows a cross-sectional view along section line IIII in FIG. 1;

FIG. 3 shows a cross-sectional view along section line IIIIII in FIG. 1;

FIG. 4 shows a partial sectional view through a gun bore;

FIG. 5 shows a partial sectional view through a cartridge chamber of agun bore and the jacket of the sabot, along section line V-V in FIG. 4;

FIG. 6 is a partial sectional view through a modified sabot projectileillustrating a modified core support system, and

FIG. 7 is a similar view showing a further modification.

The subcaliber core 1 shown in FIG. 1 consists preferably wholly orpartly of tungsten carbide and has a substantially cylindrical shapewith an ogive 2. The rear of the core 1 rests with its forward-openingcone surface 7 on a similarly shaped bore surface 8 of a sabot rear part4. This rear part 4 has a sleeve-shaped extension 5 into which the rearof the core 1 extends. A small space is provided between the rear endface 9 of the core 1, which is perpendicular to the longitudinal axis,and the base surface 11 terminating the bore 8 of the rear part 4.

The rear part 4 consists preferably of an aluminium alloy, such asPerunal. The outside diameter of the core 1 is smaller than the insidediameter of the extension 5. 70

The core 1 is provided in its rear portion with an annular groove 12.Arranged in this groove is a locking ring 14 consisting of threesegments. This locking ring 14 rests on 3,495,869 Patented Feb. 24, 1970a groove flank 13 perpendicular to the projectile axis. The outsidediameter of the locking ring is greater than the diameter of the core 1.A sleeve rests on the surface 52 of the locking ring 14 extending beyondthe core 1. This sleeve 15 consists of three equal segments. The outsidediameter of the sleeve 15 is equal to the inside diam eter of theextension 5. At its forward end the sleeve 15 has a flange 16 whichextends into an enlargement of the extension 5 and projects slightlybeyond the forward end of the extension 5.

The extension 5 is provided with annular ridges 17 which are spaced atregular intervals measured in axial direction and which are boundedforwardly by a rearwardopening cone surface 10 and rearwardly by asurface 46 intersecting the said cone surface 10. The surface 46 issubstantially perpendicular to the axis of the extension 5. From the endface, six radial slots 18 arranged at regular angular intervals extendinto the extension 5 (FIG. 3). The slots 18 extend behind the ridges 17as far as a rearward-opening cone surface 20 of the rear part 4. Thissurface 20 is intersected by another cone surface 21, extendingrearwardly and opening forwardly, the arrangement being such that thediameter of the intersection line of these two surfaces 20 and 21 issmaller than the outside diameter of the rear sleeve-shaped portion 22of the rear part 4 which, until the projectile is fired, remains insidethe mouth of a carriage, not shown. The cone surface 21 intersectsanother rearwardly extending and opening cone surface 23, which isintersected by a cone surface 24 which encloses substantially the sameangle with the forwardpointing projectile axis as does the cone surface21. This surface 24 intersects the jacket surface of the portion 22 ofthe rear part 4.

The cylindrical portion of the core 1 not extending into the extension 5is encompassed by a full-caliber jacket 25 made of plastic material andextending to a point forward of the rear end of the ogive 2. The jacketis preferably made of a thermoplastic material designated nylon 6.6,having the following properties: tensile strength 8 kp/ mm. modulus ofelasticity E 17,000 kp./cm. compressive strength 11 kp./mm. notch impactstrength 130 cm.kp./crn. elongation to rupture 200%.

The forward portion of the jacket 25 is cylindrical; the rear portion isa truncated cone slightly tapering forwardly. The diameter of theforward edge of the truncated cone is greater than the diameter of thecylindrical jacket portion so that the rear portion clearing thecylindrical surfaces forms a collar-shaped extension 26 of the jacket.This extension 26 represents the driving band intended to transmit tothe jacket the spin imparted by the surfaces of the lands 28 boundingthe grooves 29 of the gun bore 27.

As shown in FIG. 5, before firing, the jacket surface of the drivingband 26 rests against a cone surface 31 of the gun bore 27, which formsthe rear termination of the lands 28 and into which the bottoms of thegrooves 29 extend. The cylindrical jacket portion is centered and guidedby the lands 28. The rear portion 33 of the bore of the jacket 25 isenlarged, and the bore step forming a shoulder 34 rests on the end faceof the sleeve flange 16. The ridges 17 of the extension 5 have a largerdiameter than the portion 35 of the bore of the jacket 25 and engage itin barb-like fashion, The rear portion of the bore of the jacket is sodesigned that it rests against the surfaces 20, 21, 23, 24 of the rearpart 4, so that its rearmost portion touching the surfaces 23 and 24forms a ring 47 of tongue-shaped cross-section.

As shown in FIGS. 1 and 2, radial grooves 36 are cut into the jacket 25at regular angular intervals from the bore wall and extend from the endface to the level of the rear end of the extension 5. The surfaces ofthe jacket 25 terminating the grooves 36 at the rear are arranged in thesame plane as a groove 37 running round the whole periphery of thejacket and provided with a rounded bottom. The jacket 25 is provided onthe outside with recesses 38, which serve weight-reducing purposes andwhose bottoms are rounded in circular fashion and whose flanks 39enclose a substantially right angle. The symmetry planes of theserecesses 38 forming radial planes are arranged between the symmetryplanes of the grooves 36 (FIG. 2).

A plastic hood 40 extending forwardly from the jacket 25 is formed as ahollow body having a tapering forward portion and a rear portionwidening rearwardly in bell fashion to the outside diameter of thejacket 25 of the sabot 3. The hood 40 ends forward of the ogive 2 of thecore 1, enclosing the ogive and spaced therefrom and is connected withthe jacket 25 by a flange 41 which terminates it at the rear whichprotrudes inwardly to engage a groove 42 cut round the wholecircumference of the jacket 25. The hood 40 is closed forwardly by athin cover 44 arranged across its longitudinal axis and located at ashort distance rearward of the end face 43 and made integral with therest of the hood. The circular junction 45 of the cover 44 with the hood40 forms a place of intended rupture. This cover 44 increases thestrength of the hood-40 and also prevents any foreign matter frompenetrating between it and the ogive 2 of the core 1.

The action of the sabot projectile before and at firing is as follows:

In the handling and transport of the sabot ammunition, the shocksdirected towards the ogive 2 of the core 1, often consisting of a thinballistic hood, are absorbed by the hood 40, but, owing to the stiffnessof the latter, are not transmitted to the ogive 2.

When a cartridge, fed by the action of the gun, comes to a sudden stopin the cartridge chamber at the end of the loading process, the core 1,owing to its forwarddirected inertia, comes to rest with its rear grooveflank 13 against the locking element 14, and this against the sleeve 15,for whose flange 16 the shoulder 34 inside the jacket 25 forms anabutment. The force of inertia of the core 1 is transmitted by thejacket 25 to the ridges 17 of the extension of the rear part 4 and thusabsorbed by the latter. This prevents the jacket being unduly stretchedand ripped apart.

At the beginning of the movement of the projectile, after the ignitionof the propellant charge, when the driving band 26 is moving along thecone surface 31 of the cartridge chamber, its part marked by doublehatching in FIG. 5 undergoes partly plastic and partly elasticdeformation. At the same time the lands 28 of the gun bore cut into thedriving band 26, so that the side surfaces 30 of the lands 28 impartforces to the jacket 25 causing the latter to spin, The rear portion ofthe driving band 26, which suffers the greatest deformation, is arrangedin axial direction on the level of the cone surface 21 of the rear part4. The pressure developed by the elastic deformation of the driving band26 and transmitted to the jacket 25 by the cone surface gives rise to africtional force which transmits the spin of the jacket 25 to the rearpart 4. This coupling action between jacket 25 and rear part 4 can beimproved by knurling 48 of the cone surface 21 as indicated by adash-dotted line on the right of FIG. 1, causing the jacket 25 to meshwith the rear part 4 under the external pressure acting on the jacket,

The radial prestressing of the driving band 26 offers the furtheradvantage that the projectile will still be properly guided and setspinning even when the bore 27 is worn and thus has an excessive insidediameter, as this diameter difference is made good by the elasticexpansion of the driving band 26.

In the acceleration of the sabot projectile, the core 1 is pushed withsuch force rearwards against the chamber formed by the supportingsurface 8 of the rear part 4 that the latter undergoes plasticdeformation. As a result the subcaliber core 1 moves relatively to therear part 4 rearwards and is then no longer held free of clearance inaxial direction. Further, the core 1 is set spinning by the frictionalforce acting between it and the rear part 4.

The force acting on the jacket 25 in axial direction forwardly isdetermined by the size of its surface exposed to the gas. At thebeginning of the projectile movement, this surface is composed of therear annular surface 49 and, as the gas can penetrate between thesurface 24 of the rear part and the jacket surface 50, of the surfacewhich is determined by the projection of this jacket surface 50 on to aplane perpendicular to the projectile axis. The relations are such thatthe acceleration which can be imparted to the light jacket 25 by thisgas power is at least equal to the acceleration sustained by theprojectile relieved of the weight of the jacket 25 and the hood 40. Thedanger of any displacement of the jacket 25 with respect to the rearpart 4 is countered by the anchoring of the jacket in the rear part. Thesecuring is ensured by the fact that the rearmost portion of the jacket25 is designed as a forward-closing key ring which is clamped betweenthe surface 31 or between the lands 28 and the groove bottoms 29 on theone side and the surface 21 of the rear part 4. A gas force acting onthe surface 50 of the jacket forces the ring 47 with sealing effectagainst the surface 23 of the rear part 4. This arrangement prevents thegas from penetrating between ring 47 and surface 23 and thus undulyenlarging the gas hit area of the jacket and, accordingly, the gas forceacting on the jacket in axial direction.

Under the pressure acting on the cover 44 of the hood 40 inside the gunbore 27 at firing, the cover 44 is separated from the hood 40 at theplaced of intended rupture 45 and thrown rearwards, so that the pressurenow also acts on the inside of the hood. With increasing spinning speed,the hood 40 is ripped apart by the centrifugal force acting on it, andthe fragments settling against the gun bore 27 are pushed out of itforwards by the jacket 25.

Once the projectile has left the barrel, the centrifugal force causesthe jacket 25 to disintegrate into segments moving radially outwards,and this is aided by places of intended rupture formed by the webs 51bounded by the bottoms of the grooves 36 and the surface of the jacket25. The said segments detach themselves from the rearmost portion of thejacket 25 anchored in the rear part 4 substantially along a planeperpendicular to the projectile axis and containing the ring groove 37.Under the action of the centrifugal force also, the segments of theextension 5 of the rear part 4 which are bounded by the slots 18 andwhich are additionally subjected to the centrifugal forces acting on thesegments of the sleeve 15 and the locking element 14 are torn from therear part 4 and hurled from the core 1. The said core is then completelyfree and, as it presents less resistance to the air than does the rearpart 4, moves forward independently of the latter.

In a further example as shown in FIG. 6, the foremost portion of theextension 5 of the rear part 4 is curled inwardly (53) and rests againstthe flange 16 of the sleeve 15. With this arrangement, the inertia forceacting on the core 1 when the cartridge is fed into the cartridgechamber is transmitted not to the jacket 25, but direct to the extension5, i.e. to the rear part 4, thus dispensing with the need for ridges 17on the extension 5. This also applies in the third example as shown inFIG. '7, wherein the sleeve 54 is screwed up with the extension 5bearing the thread 56. From the end face, slots 55 are cut into thesleeve 54 at regular angular intervals. These slots form the boundariesof segments into which the sleeve 54 disintegrates at firing under theaction of the centrifugal force.

The elements 14 and 15 in FIGS. 1 and 6 for the support of the core .1can also be united to form a single securing body. Such a body hassubstantially the same cross-section as the two elements 14 and 15together and is also split into several segments of equal size.

I claim:

1. Sabot projectile comprising a projectile core (1) which extends alongan axis, a sabot (3), (4, 25) with an approximately cylindrical rearpart (4) having on its circumference a groove (21, 23, 24), said groovedefined by two spaced substantially parallel side walls (21, 24) and aflat bottom surface (23) connecting said side walls (21, 24), said sidewalls being annular portions of imaginary cones having apices pointingrearwards in relation to the direction of flight, said sabot (3), (4,25) having a jacket (25) encompassing the projectile core (1) andfitting into said groove (21, 23, 24) to form a gas tight connectionbetween said jacket (25) and said rear part (4) and a driving band (26)integral with said jacket (25) located in the area of said groove (21,23, 24) in the rear part (4) to improve the tightness between saidjacket (25 and said rear part 4).

2. Sabot projectile comprising a projectile core (1) extending along anaxis, a sabot (3, 4, 25) with an approximately cylindrical rear part (4)having a groove (21, 23, 24) on its circumference, said groove definedby two spaced substantially parallel side walls (21, 24) and a flatbottom surface (23) connecting said side walls (21, 24) said side wallsbeing annular portions of imaginary cones having apices pointingrearwards in relation to the direction of flight, said sabot (3), (4,25) having a jacket (25) encompassing the projectile core (1) saidjacket (25) having on its rear part pointing in the flight direction ofthe projectile two spaced substantially parallel surfaces being annularportions of imaginary cones having apices pointing rearwards, both ofsaid surfaces contacting the side walls (21, 24) of the groove (21, 23,24) of the rear part (4), said jacket (25) having a driving band (26)located in the area of the groove (21, 23, 24) of the rear part (4) toimprove the tightness between said jacket (25) and the rear part (4).

3. Sabot projectile according to claim 1 for a rifted gun bore (27)wherein the outer diameter of said driving band (26) is greater than thegreatest interior diameter of the gun bore (27) 4. Sabot projectileaccording to claim 2 comprising a locking ring (14) an annular groove(12) in the projectile core (1) Where the locking ring (14) fits in, afrnt surface (52) on said locking ring (14) whereby said front surface(52) serves as a first resting surface, and with a second surface (34)on said jacket (25) which is parallel to said first resting surface (52)of the locking ring (14) and set at a distance from said first restingsurface (52), a sleeve (15) resting on one hand on said first restingsurface (52) of said locking ring (14) and on the other hand on saidsecond resting surface (34) of said jacket (25) to prevent the axiallydisplacement of the projectile core (1) in relation to the jacket (25)in one direction.

5. Sabot projectile according to claim 4, wherein said jacket (25) ofthe sabot (3) has a bore step (34), which forms said second restingsurface of the jacket (25) and a flange (16) on said sleeve (15) whichrests against said second resting surface (34) of the sabot (25).

6. Sabot projectile according to claim 4 wherein said rear part (4) ofthe sabot has an extension (5) and said extension has a shoulder (53)which constitutes said second resting surface of the sabot (3, 4, 25).

7. Sabot projectile according to claim 6 wherein said extension (5) ofthe rear part (4) has annular ridges (17) of saw-tooth shapedcross-section, whereby the annular ridges (17) form an additionalconnection between the rear part.( 4) and said jacket (25).

References Cited UNITED STATES PATENTS 2,669,930 2/1954 Darby et al.10293 3,096,715 7/1963 Dufour 10293 X 3,349,712 10/ 1967 Schwager et al.102-93 FOREIGN PATENTS 1,298,756 6/ 1962 France.

573,914 12/1945 Great Britain.

586,174 3/ 1947 Great Britain.

752,448 7/1956 Great Britain.

150,557 6/1955 Sweden.

351,522 2/1961 Switzerland.

ROBERT S. STAHL, Primary Examiner

